Method of producing a coating composition



Patented Dec. 4, 1945 METHOD OF PRODUCING A COATING COMPOSITION Glarence M. Carson, or to Wingfoot Guyahoga Falls, Ohio, assign Corporation, Akron, Ohio,.. a: corporation of Delaware N Drawing. Application. March ,20, 1942, Serial No. 435,474

3. Claims.

This invention relates, to the 'method of producing coating compositions fromarubber derivative, It relates more particularly to a coating composition containing a. partially oxidized. rubr, derivative. The application. is in part a continuation of my. application. Serial No. 311,945.

filed December 30, 1939;

The rubber derivatives used in carrying out this invention are partially oxidized cyclized rubbers. These may be prepared by treating rubber with various condensing or cyclizing agents. For example, the halide of an amphoteric metal or chlorostannic acid or a combination of two or more reagents may be causedto-react with rubber under controlled conditions to produce the desired rubber derivatives.

Phosphorous oxychloride or boron fluoride may be used as the condensing agent. The rubber derivatives may be formed in the manner-disclosed by Sebrell U. S. Patent #2,052,'423- and Endres U, 'S. Patent 112,052,391. 7

The cyclized rubber used in carrying outthe invention is partially oxidized. The cyclization may be carried out by treating a. solution of milled rubber with a reagent, such as chlorostannic acid ortin tetrachloride. The reaction mixture is emulsified with water, and then by steam distilling the solvent from the emulsion thus produced the rubber derivative is precipitated. The dried product obtained in this way varies in chemical properties depending upon the extent of the cyclization, the temperature at which emulsification takes place, the chemical structure of the emulsifying agents and the pH value of the water. The product usually obtained by the use of tin tetrachloride and hydrochloric acid is a yellowish-white powder of a varying degree of particle size but containing a; small proportion of material insoluble in coal tar solvents, such as toluol or in petroleum solvents, such as "rubber solvent gasoline. Such solutions are clay-colored and cloudy in appearance due to suspended, insoluble matter.

By the process of mil1ing,,i. e., by passing the powder of the rubber derivative repeatedly or continuously through steel rolls the powder is massed. into atsheet which, when cooled, may be ground. into. particles the size of a small bean, dark brown to yellowin color. These particles arereferred. to herein aspelletsh They are easily di'spersed'imcold toluol or gasoline giving, a much clearer solution than the unmilled powder. When a solution of the unmilled material is applied to paper it is rough or gritty due, to the insoluble matter in it: Milling the oxidized resin (the oxidized portion is really insoluble in all solvents) disperses the oxidized portion to such a degree that" the, solution is practicallyclear. However,

on longstanding (for example, three months).

, the oxidized portion will settle out. Whereas theunmilledpowder in toluol forms a solution too viscous to be applied easily-to a material, such as paper. by a dipping or rollerapplication, the

milled, material is of much lower viscosity and.

readily lendsitself' to such applications.

By varying; thetime of the cyclizing' reaction or. theamount ofcyclizing-reagents used; product's having a rang of distortion points. from 5: to.

125. C. have been preparedand marketedfor= varioususes. The distortion point is determinedfl asfollows:

The driedreaction, product in itsunmilled orpowdered state: is molded by heat and pressureinto a sheet ten inchessquare andone-eighth. inch thick. From this-sheet; strips one-inch wide are cut; These are immersed in; a water bath on two fulcrums one inch highand eight inches apart; The temperature of the water bath is raised 1 C: per minute. strip ofmolded'sheet ispushed down at themld point between the fulcrumsuntilit touches the bottom of the bath; Thepressure-is immediately released. When the strip softens to-- the point where it does not return to its original straight position the, temperature is noted, and this. is called the distortion point;

Th oxidized cyclized products usedirecarryingout this invention contain about 1 or- 2 or 3% of oxygen. The oxidation may be efiected in any. one of several ways; For example, thereacted cement may be oxidized by passingoxygen through it. Chemicals, such as'hydrogen peroxide, ammonium persulfate or chlorinated lime, etc may, be used'toaceelerate the oxidation. According to another method of oxidizing, the: dried and milled rubber derivative; either in sheet form or as pellets preferably varying in size=from that retained by a l'0'-mesh-per-inchscreento that which completely passes through a 2'-meshperinch screen, may be heated in air or oxygen gas under carefully controlled conditions.

For example, the substantially unoxidizedprod ucts which are precipitated on distillation of solvent? from the water emulsion, and which then have distortion points offrom 5 t060 0;, are milled; The resulting milled-sheet is ground into pellets of a particle size-of'the order aboveindicated: The-ground product is placed in trays one inchdeep and? heatedfrom six to eighteen hours by circulating air at- 1-75-- F: merit. The length At each minute the of 75 C. may require thirty-six hours at 175 F,

oxidized product resulting from as above described, is not enspirits or other petroleum I I The granular oxidation in a tray, tirely soluble in mineral solvents. It is more nearly solublein benzene, toluene and other coal tar solvents. By milling this oxidized product and grinding, a granular product is obtained which is quite dispersed" in mineral spirits, benzene and toluol, and on dispersion therein, produces a practically clear solution. or suspension,

To .test the degree rolled or shaken in a of oxidation the pellets are bottle containing 2 parts of the pellets and 80' parts of toluol for sixteen hours. The presence of some insoluble lumps indicates that oxidation is suflicient.

According to another method of oxidation 5% of chlorinated lime, Ca(OCl)Cl, the bleaching powderof commerce, is milled into 95% of the milled cyclized product witha distortion point of 100-125 C, The milling time is approximately fifteen minutes, oxidation taking place on the mill. The product is soluble in gasoline or coal tar solvents. The value of the product is shown in its use as a moisture-vapor-proof coating for labels on food packages. The unoxidized Pliolite, applied over heavily inked labels and dried in an oven for forty-five seconds at 150 F. has poor adhesion. By the oxidation process described above, the adhesion is very much improved.

The oxidation occurs largely on the surface of the, pellets. Uniformity of the product is obtained by later milling the pellets to uniformly disperse the oxidized material throughout the whole body of the material. An antioxidant may be milled into the rubber derivative at this point.

The resulting milled sheet is then allowed to cool and is then ground. 7 v

The oxidized product may be dispersed in various solvents, such as toluol, gasoline, hydrogenated gasoline, benzol, carbon tetrachloride and various mixtures of the above or similar solvents. The solution viscosity is relatively high. By milling the oxidized rubber derivative and thereby dispersing the outer oxidized shell of each particle throughout the balance of the rubber derivative, a more easily soluble and lower viscosity product is obtained. If an antioxidant is to be used with the rubberderivative, it may be dissolved or dispersed in the solvent together with the rubber derivative.

It has been found has greater adherence that the oxidized material to certain types of surfaces than the unoxidized material. When the unoxidized material, in admixture with wax, for example, is coated onto nitrocellulose film, aluminum foil or glassine paper or the like, and two portions of the coated sheet are united by heat-sealing, as in the formation of a package, the seams will be weak, On breaking or tearing the seal the coating will show poor anchorage to the base material and weak strength in itself. However, if the resin is oxidized to the proper degree for theparticular base material, the anchorage will be improved, and the strength of the seal will be much better. This improvement in' adherence is noticed in coating the following. materials, which are listed in the order in which the improvement is most noticeable: nitrocellulose, aluminum foil, oxidized inks (as on labels which have been printed for several weeks, particularly black and blue inks), polyvinyl alcohol sheet, cellulose acetate sheet, calendered kraft paper, rubber hydrochloride film, uncoated regenerated cellulose (Cello- 1 phane), glassine, ethyl cellulose foil, casein sheet,

bond or book paper, parchment and other roughsurfaced papers.- 7 r The oxidized products when coated on paper or any of theabove-mentioned sheets may lose their moisture resistance, their flexibility and their ability to heat-seal at low temperatures, and they may take. on undesirable characteristics if exposed to ultra-violet light. The presence of oxidation inhibitors prevents or tends to prevent any change taking place in the product on aging. The best oxidation inhibitors are not those commonly used in the rubber industry, but rather those which have been found to be the best for prevention of gum formation in gasoline. However, the secondary aliphatic amines and the water insoluble derivatives of hydroquinone also have been found to prevent rapid aging. Some representa-' tive inhibitors are:

Aromatic and heterocyclic bases:

o-Amino diphenyl p-Amino diphenyl Diamino diphenyl methane p-Phenylene diamine p-Amino dimethyl aniline o-Toluidine Benzamide n-n Di(o-methyl cyclohexyl) -piperazine Secondar aromatic amines:

Diphenyl-p-phenylenediamine Phenyl-o-tolyl-phenylenediamine p-l-Iydroxy diphenyl amine Aminophenols o-Aminophenol p-Aminophenol Mono-benzyl-p-aminophenol 2-Amino-5-hydroxytoluene Phenols, naphthols and ethers:

Butyl hydroquinone Pyrocatechol Alpha-naphthol I Hydroquinone-monobenzyl ether (Agerite Alba) Veratrole Diamyl hydroquinon'e Various plasticizers or modifiers may be added, such as: i i

tops, purifid as mar residue,

(d) synthetics: y Vinylite, Neville resin, Aroclor, AWII, RH-

35, Petrex 59-71, Petrex-all, Beckacite, Beckasol, Berex, sucrose octa-acetate, Vistanex-all, Amberol ST-137, triphenyl phosphate, Santicizers, vinyl acetate (Gelva resin).

(e) Liquid plasticizers:

Tricresyl phosphate, dibutyl phthalate, amyl stearate, Hercolyn, Abalyn, glyceryl butyl phthalate, glyceryl abietate, diamyl naphthalene, mono-amyl naphthalene, ethyl lactate, butyl stearate, ethylene glycol, tributyl citrate, dibutyl sebacate, Cardolite, lauryl alcohol.

Plasticizers which have oxidation-inhibiting value include glycerol mono stearate, 2: '7 hydroxy naphthalene and amino stearin.

The modifiers or plasticizers may advantageously be milled into the rubber derivative before the rubber derivative is subjected to oxidation,

1 Phenolics, such as Durez, Beckacites and other itors or antioxidants. From one to four per cent of anti-oxidant ma be milled into the oxidized cyclized rubber, thus preventing further oxidation on storage or after coating, or the anti-oxidant may be separately added to the coating com- Position.

For example, it is advantageous to oxidize the cyclized rubber, which has a 5060 C. distortion point, in the preparation of compositions which are to be applied to glassine paper in packaging foods. It is advantageous to partiall oxidize the rubber derivative when it is to be used as labels for tin or cardboard cans, packed for shipment in cartons or boxes, because the oxidized product will not scuff or become defaced as readily as the unoxidized product when the packages rub together during shipment. The unoxidized rubber derivative has relatively poor adherence to nitrocellulose coated foil or to nitrocellulosecoated paper. However, if it is oxidized prior to being compounded into a coating or adhesive for adherence to nitrocellulose, the adhesion will be improved.

The following examples illustrate the invention:

Example 1.Coating for cellulose acetate Parts Oxidized rubber derivative 15.0 Parafiin 134 S. P 1.5 Gum dammar 1.5 Diamyl naphthalene 1.4 Vanox .6 Toluol 80.0

By dissolving the rubber deriva Vanox consists of .5 of pyrogallol, 0.25 part hydroquinone and 0.25 part triethanolamine. This gives a satisfactory coating for cellulose acetate which retains its resistance to moisture-vapor transmission and its heat-sealing properties for a prolonged period.

Example 2.Pliolite paper coating Parts Oxidized rubber derivative 15.8 Paraflin wax S. P.) 1.8 cyclohexanon resin 1.4 Diamyl naphthalene 0.8 Vanox 0.2 Solvent 80.0

By dissolving the Pliolite, paralfin, cyclohexanone resin (which may be Resin AWlI) and the other above ingredients in toluol or gasoline, a coating for glassine paper, cellulose acetate sheet and the like is obtained. These sheets may be coated by being dipped in the solution.

Example 3.-C'oating for metal foil Parts Oxidized rubber derivative 15.0 Parafiin 148-50 F 1.5 n-n-di(methylcyclohexyl) piperazine 0.6 Rubber solvent gasoline 82.9

Example 4.--Modified coating for regenerated cellulose and for cellulose acetate Parts Oxidized rubber derivative 15.0 Gum dammar 1.5 Parafiin (148-50" F.) 1.5 Mono-benzyl-p-amino phenol 0.3 Toluol 81.7

What I claim is:

1. The process of producing a coating composition which comprises oxidizing the surface of a pellet of finely divided particles of a. cyclized rubber, milling the oxidized pellet and an anti-oxidant and dispersing the milled product in a solvent.

2. The method of producing a coating composition which comprises oxidizing the surface of a pellet composed of finely divided particles of a c clized rubber, milling the pellets to disperse the oxidized material throughout the mass and then dissolving the milled product and an antioxidant in a solvent.

3. In the method of producing a coating composition from a cyclized rubber obtained by prea solvent.

CLARENCE M. CARSON. 

